The only reason we don't walk with bent knees is because that uses a lot of energy and can only lock our knees one way, but we do that sometimes for better movement, like when fighting or doing some sports. hydraulics are fundamentally different. The new Atlas seem to keep the legs fairly straight when standing/moving but the video is too short to come with larger conclusions.

Tesla is working with a large difference in approaches from Boston Dynamics. I think they can achieve some success even with the fact that their robots are not as good as the others by using the "pasta to the wall" strategy they seem to use. They made lots of the robots already and that can lead to someone finding a good use case for them even with lots of limitations. BD did this with spot to some success.